In the manufacturing industry for producing oven-baked products of small thickness, for example biscuits, it forms part of the known art to subject the products, at output from the baking step, to a series of operations in which the products coming from an oven are selected, grouped together in stacks and, for their transfer, set “edge on”, i.e., withheld during the conveying process, thanks to appropriate guides and sliders, in such a way that they rest their side surface (edge) on the surfaces of the conveyors. The aforesaid mode of transfer has proven to be the most effective both on account of the high rates of production rendered possible, and on account of the low rate of rejects that it involves.
After the step of grouping the products together into cylindrical stacks, the stacks are caused to advance in a direction transverse to their own axis, which is thus substantially horizontal, and are subsequently induced to translate in a direction coincident with said axis, so as to enable packaging of each stack by means of a synthetic film.
In particular, the packaging step envisages that the stack will be wrapped laterally in the film and then the latter will be sealed at the side, and subsequently in a position corresponding to the bases, in order to obtain the packet.
In order to vary the relative direction of advance of each cylindrical stack, it forms part of the known art for the conveyor set upstream, designed to translate the stacks in a direction orthogonal to the generatrices of each cylindrical stack, to be set in a position corresponding to its output portion orthogonal to the conveyor set downstream, which is designed to translate the stacks in a direction parallel to their generatrices. In this way, the stacks at output from the conveyor set upstream may be transferred directly, for example by gravity or by means of a percussion or pusher device, onto the conveyor set downstream, given that no absolute change of direction of the longitudinal axis (i.e., the one parallel to the generatrices) of the stacks is required.
The European patent application EP-A-0 084 763, in the name of CAVANNA, describes a plant for the conveying of biscuits towards a packaging machine. The CAVANNA system is provided with a continuous belt conveyor for biscuits, which are moved in a direction orthogonal to their longitudinal axis, which, in its terminal portion, extends at right angles above a conveyor belt with sockets designed to convey the biscuits in a direction coincident with their longitudinal axis. The biscuits at output from the top continuous belt are induced to drop into the sockets of the bottom belt. The CAVANNA patent application suggests the use of said system for generic products of cylindrical shape.
The above embodiment, albeit somewhat simplified mechanically, presents a number of drawbacks. In the first place, the oven-baked products of small thickness, owing to their somewhat brittle nature, in the passage, in general by gravity, from the top belt to the bottom one may get broken or chipped, with the consequent production of packets of biscuits that are not suitable for the market. Moreover, for the biscuits to fall exactly into the seats (sockets) provided, it is necessary to synchronize carefully the speed of advance of the top belt with that of the bottom conveyor belt, this generally involving both a limitation of the maximum speed achievable, and the necessity of calibrating the system with a certain frequency.
Finally, in the case where the plant described in the application EP-A-0 084 763 were used for conveying stacks of oven-baked products resting on edge, which is, on the other hand, an eventuality that is not explicitly contemplated in the text of the CAVANNA patent application, it would be necessary- to carry out an extremely precise synchronization and an accurate and frequent control of said synchronization in order to prevent the products set on edge (biscuits) of each stack from bumping against the baffle plates that define the sockets during their transfer, or in order to prevent a number of said products from dropping outside the sockets instead of inside. Furthermore, the CAVANNA plant does not enable alternative geometrical dispositions of the top conveyor belt with respect to the bottom belt, other than the arrangement at right angles envisaged, above all if in said plant it is intended to use products conveyed on their edges.
For the transfer of stacks of biscuits set “edge on” from a top conveyor belt to a bottom conveyor belt, in which the latter is provided with shaped seats within which the stacks are to be housed, there is known the solution proposed in the U.S. Pat. No. 4,627,215 in the name of SIG. The SIG patent envisages the presence of an orbital transfer device operatively set between the two conveyors and provided with a plurality of gripping assemblies within which each stack is set in a position corresponding to the belt conveyor set upstream and is hence drawn, on a special sliding surface, towards the seats of the belt set downstream.
The SIG transfer device, however, does not envisage that the conveyor set downstream causes the stacks to advance in a direction parallel to their axis, and hence does not enable orientation of the stacks in a different way with respect to the direction of advance in the passage from the conveyor set upstream to the conveyor set downstream.
The absence of any indication in the SIG patent regarding the possibility of orientation in a different way of the stacks of biscuits when they are passing from one conveyor to the other points to the fact that that the person skilled in the sector, specifically in the case of variation of the direction of conveying of the cylindrical stacks with respect to their generatrices, would not have received therefrom any suggestion to use an orbital conveyor and would thus not have used the aforesaid disposition at right angles of the conveyors set upstream and set downstream as described in the CAVANNA patent application. Furthermore, the impossibility of orientation of the stacks during transfer, as well as the geometry itself of the SIG transfer device, enables either only intermittent or else perfectly synchronized operation of the equipment. In fact, the conveyor set downstream must advance, at a rate dictated by the width of the seats, so as to present the subsequent empty seat in a position corresponding to the position of disengagement of the stack from the gripping assembly of the transfer device, must stop, and can resume its advance only when transfer of the stack has taken place.
A purpose of the present invention is to provide a method for the transfer of cylindrical stacks of oven-baked products resting on their side surface or edge, i.e., in which the products making up each stack are resting on one of their edges, from a conveyor in which the stacks advance in a direction orthogonal to the generatrices of their cylindrical shape, to a conveyor in which the stacks advance in a direction parallel to or coincident with said generatrices, which will enable a high speed of production, without thereby causing damage to the products in the stacks.
Another purpose of the present invention is that of providing, in a plant in which the cylindrical stacks of oven-baked products are resting on their side surface, a transfer device for transferring stacks between a conveyor set upstream, which translates each stack in a direction orthogonal to the generatrices of the cylindrical shape, and a conveyor set downstream, in which the stacks are caused to advance in a direction parallel to said generatrices, which will be particularly effective and which will not present the disadvantages of the known art described above.
A further purpose of the present invention is that of providing an equipment for the treatment of oven-baked products arranged in cylindrical stacks, in which said stacks are resting on their side surface during their advance, which will be rapid, which will not require a high precision of synchronization between the conveyor set upstream and the conveyor set downstream, and which will be particularly precise in the conveying operation so as to minimize the breaking or chipping of the products conveyed.